The invention is directed to the press-forming of glass articles having lip areas from molten glass. Conventionally, the method of press-forming articles from molten glass or glass-ceramic materials includes the use of a mold for forming the outer surfaces of the article, a plunger for forming the inner surfaces thereof, and a mold ring which limits the upper movement of the glass between the mold and the plunger and forms an upper edge on the article. In practice, a small amount of glass or glass-ceramic, called a gob, is first deposited in the bottom of the mold and with the mold ring in position, the plunger is moved downwardly within the mold thus forcing the gob of semimolten glass upwardly within the cavity formed therebetween to the limits of the mold ring, and thus form a pressed article.
In the case of articles which are essentially symmetrical or have a shape generated by surface of revolution, the molten glass arrives in contact with the mold ring substantially simultaneously about the upper edge of the article. However, when forming very asymmetrical articles such as a casserole with an integral handle as shown in FIGS. 2a and 2b, various problems arise with regard to both the forming of the lip portion and the simultaneous distribution of glass to the mold ring. That is, if the lip is not formed correctly, an unsightly fin is produced adjacent its inner edge, and when the glass distribution to the upper edge of an asymmetrical vessel is not correctly programmed, either an extended portion on such vessel will be poorly completed due to a shortage of material, or the lip will be defective because of excess material. Such excess material, if it arrives at the lip portion while still in a flowable condition will produce excessive fins, whereas if such glass became solidified during forming, the pressure of the plunger wound tend to crack the lip making the articles unuseable.
Accordingly, the present invention has overcome the problems of producing fins on lip portions and incomplete filling during the pressing of asymmetrical articles by not only offsetting the area in which the fin will be formed, but also by programming the distribution of molten glass to the upper edge of the article so as to uniformly fill the mold cavity and distribute glass to the upper edge portions of the article formed therein.